Arsenal 4 Watford 0

Arsenal gained revenge for their FA Cup defeat three weeks earlier as they flattened the hapless Hornets in a one-sided contest at Emirates Stadium.

The home side kept their title hopes alive with a comfortable win against Watford – who looked a pale shadow of the side that deservedly broke the Gunners’ grip on the FA Cup on their previous visit to north London.

Alexis Sanchez fired Arsenal into an early lead before Alex Iwobi scored his second goal in as many Premier League starts, ex-Watford loanee Hector Bellerin added the third and substitute Theo Walcott wrapped up a resounding win.

It took Arsenal just four minutes to seize the advantage as Iwobi swept in a cross for Sanchez, whose header was parried by Heurelho Gomes – but the Chilean reacted first to tuck home the loose ball.

The early goal helped to settle the Gunners and they continued to put Watford under pressure, with Sanchez, Iwobi and Danny Welbeck all teasing holes in the visitors’ defence.

Gomes kept out Iwobi’s effort with an acrobatic tip-over save, as well as diving to turn a Sanchez free-kick around the post, while Welbeck’s drive spun off Sebastian Prodl and into the side netting.

Watford, who looked like a side thoroughly distracted by their Wembley trip in three weeks’ time, offered virtually nothing in reply, with David Ospina scarcely required to break sweat in the first half.

And the Gunners went 2-0 up seven minutes before the break, with Sanchez finding space and returning the compliment by way of a square pass to Iwobi, who drilled it first time into the net.

Watford made two substitutions in an attempt to turn the tide, but it made little difference as the home side extended their lead just three minutes into the second half.

Bellerin set up Sanchez for a cross that was headed out by Allam Nyom and fell perfectly for the Arsenal right-back to strike a volley that took a deflection off Ben Watson and wrongfooted the goalkeeper.

The Hornets were fortunate to avoid further damage in the aftermath of the third goal as Iwobi cracked a drive against the crossbar and Sanchez and Welbeck both brought saves from Gomes.

Belatedly, Watford mustered something resembling an attempt at goal as Prodl’s header was nodded off the line by Nacho Monreal before Deeney turned Laurent Koscielny and forced a flying stop from Ospina.

But the contest had long since been decided and the only remaining question was whether Arsenal could equal their biggest margin of victory for the season.

The answer was yes, although they had to wait until the final minute to do it as Joel Campbell galloped past Nyom and cut the ball back for fellow substitute Walcott to steer home.